Failing Grades

A letter in response to David Denby’s article (November 19, 2012)

As the parent of two public-school students, I read David Denby’s article on Diane Ravitch’s efforts at school reform with great interest (“Public Defender,” November 19th). I am agnostic on the so-called reform movement, and have no great love for teachers’ unions or the tenure system, but one of Ravitch’s opinions bothered me immensely: to say that value-added modelling is “junk science” because “many factors can affect students’ test performance” is not quite right. Of course, students might do well or poorly on tests in any given year owing to factors that have nothing to do with their teachers, but each teacher will have twenty-five or so data points every year. If one or two students are outliers, or if all students in every grade level at a certain school do poorly one year—as, for example, one might expect in the aftermath of a natural disaster—then teachers should not be penalized. But if, year in and year out, a teacher’s students consistently under- or overperform with respect to predictions, one can rightly assume that some significant proportion of student performance is the result of that teacher.

Josh Miner

La Crosse, Wis.

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